Process for bleaching unbleached cellulose

ABSTRACT

UNBLEACHED CELLLOSE IS BLEACHED TO A GOOD DEGREE OF WHITENESS WITH LOW DEGRADATION AND WITH REMOVAL OF ANY SIZE OR COTTON HUSK PRESENT, BY A CONTINUOUS PROCESS INVOLVING SUCCESSIVE CONTACT WITH (1) AMYLASE, (2) A COMPOUND SUCH AS TRICHLOROISOCYANURIC ACID CONTAINING A NITROGEN-CHLORINE LINKAGE, AND (3) AN OXIDATIVE BLEACHING AGENT.

a s t 572. as? i 3,572,987 Patented Mar. 30, 1971 hour. Thus, if thefabric moves at a 100 meters per min- 3,572,987 ute, 6,000 meters offabric, which may weigh more than PROCESS FOR BLEACHING UNBLEAC a ton,can be held up in the J-box. While it is possible to CELLULOSE reducethe time required for the bleach to act by adding Hubert Grunow,Bagneux, France, assignor to Entreprise Miniere et Chimique (formerlyOffice National Industriel de lAzote), Toulouse, France No Drawing.Filed May 23, 1968, Ser. No. 731,640 Claims priority, applicationFrance, May 24, 1967,

1m. or. 15061 3/06 US. Cl. 8-101 9 Claims ABSTRACT OF THE DISCLOSUREThis invention relates to the bleaching of unbleached cellulose.

Any satisfactory process for bleaching unbleached .cellulose textilematerials, especially those that contain synthetic fibers, must not onlybleach the cellulose, but must also remove any cotton husks any sizewhich may be present, increase the hydrophilicity of the fiber, and notlead to any substantial degradation of the cellulose mole- "cules.Certain enzymatic materials, such as amylases, are known effectivedesizing agents for textile materials, but have no bleaching effect, anddo not remove cotton husks, nor improve the hydrophilicity of thefibers. Conversely, conventional bleaching agents such as hydrogenperoxide and sodium chlorite have a good bleaching effect, but do notremove size and, in many cases, do not improve the hydrophilicity of thefibers. The hydrophilicity can be improved by boiling with highlyconcentrated sodlum hydroxide solution, but this treatment tends todegrade the cellulose, and in any case involves the use of an additionalprocess step. At the present time, it is generally necessary inindustrial practice to subject the cellulose material to be bleached toa succession of different treatments which are applied discontinuouslyand which require large apparatus and a considerable amount of time.There therefore a need for a process which can be operated continuouslyat high speed which not only bleaches cellulosic textile fabrics, butalso removes any cotton husks and size which may be present, increasesthe hydrophilicity of the fibers, and does not degrade the cellulose toany substantial degree.

The present invention provides such a continuous process for bleachingunbleached cellulose, which process comprises contacting the saidunbleached cellulose with,

in the following order, (1) amylase, (2) a compound con- .taining one ormore nitrogen-chlorine linkages, and (3) a conventional oxidativebleaching agent. This new process can be operated continuously at highspeed, e.g. at a feed rate of cellulose textile material of 50 to 100meters per minute. Surprisingly, the combination of treatments thuscarried out" gives results which are better than the sum of the resultsobtained by each treatment carried out separately. In particular, thetreatment (2) with the compound containing one or more nitrogen-chlorinellnkages activates the subsequent action of the bleach, thereby reducingto a substantial degree the time required for the latter to have itsdesired effect. This is very important industrially, as in priorcontinuous processes it was necessary to store, e.g. in a J-box, thefabric impregnated with the bleach at 100 C. for a considerable period,e.g. an

activators to the bleach, these have the effect of seriously reducingits effective life and of making the bleaching effect difficult, orimpossible, to control adequately.

In the process of the invention, the compound containing one or morenitrogen-chlorine linkages is, for example, an N-chlorinated organiccompound such as N-chlorotoluene-sulphonamide or more advantageously, achlorinated cyanuric acid. This compound is applied from an aqueous bathhaving a pH of 4 to 8 and a content of available chlorine from 2 to 20grams per liter.

While the conventional bleach may be any commercially used bleachingagent, e.g. an alkali metal chlorite or hypochlorite, best results havebeen obtained by the use of hydrogen peroxide.

The process of the invention can, if desired, be followed bya treatmentof the cellulose in an alkaline bath, and it is an advantage of the newprocess that this treatment may be very short so that the cellulosematerial is not degraded to any substantial extent.

In more detail, the new process can be carried out as follows. Thecellulose textile material, e.g. in the form of threads, tows, or wovenfabric, is passed into a conventional, caster-tank containing an aqueoussolution of commercial amylase having a concentration of 2 to 10 gramsper liter and at a temperature from 20 to C. This bath can also contain1 to 2 grams per liter of a compatible wetting agent. The materialremains in this bath for from 5 to 30 seconds, depending upon theconcentration of the amylase. It is then squeezed to 50 to wet take-up,washed with boiling water, and squeezed to 50 to 70% wet take-up. Thecellulose material is passed to a second conventional caster-tankcontaining the chlorinated derivative of cyanuric acid (or othercompound containing a nitrogen-chlorine linkage) in a concentrationgiving an available chlorine content of 2 to 20 grams per liter, at atemperature of 10 to 60 C. and a pH of 4 to 8. The cellulose materialcan remain in this tank for from 5 to 30 seconds, and be fed at a speedof up to 100 meters per minute, so that the tank can ordinarily containfrom, say, 10 to 30 meters of fabric. After leaving the second bath, thefabric is washed with hot water and squeezed.

The consumption of amylase in the first bath is generally between 0.3and 0.5%, and that of the chlorinecontaining compound in the second bathbetween 0.1 and 0.8%, the percentages being by weight of the materialbeing treated.

After the aforesaid washing with hot water and squeezing, the cellulosefabric is fed to a tank containing hydrogen peroxide stabilized withsodium silicate, or any other suitable bleach. After leaving this bath,it is squeezed to 60 to 100% wet take-up and then kept for /z to 10minutes in a J-box or a steamer at 100 C. or for /2 to 1 minute in asteamer under pressure at to C.

The material is then washed at about 100 C. in sodium hydroxide solutionhaving a concentration of 5 to 10 grams per liter, and finally washedcarefully and dried.

The concentration of hydrogen peroxide is from 1 t0 3% by weight,expressed as 130 volume (35%) hydrogen peroxide. This is approximatelythe same concentration as is prior processes. However, if it desired toreduce the treatment time with hydrogen peroxide to V2 to 2 minutes at atemperature of 100 C., the concentration of hydrogen peroxide in thetreatment bath must be increased to 4 to 5%.

An alkali metal chlorite, e.g. sodium chlorite, may be substituted forthe hydrogen peroxide. If this is done, it is necessary before thefabric is immersed in the chlorite bath to wash it very thoroughly toremove any excess of chloro-cyanuric compound which would react with thechlorite and cause decomposition of the latter. A suitable chloriteconcentration is 10 to 30 grams per liter, and the bath can contain aconventional adjuvant such as sodium phosphate. The fabric is squeezedto 80 to 100% wet take-up and then kept at a 100 C. ifor to 15 minutesbefore being Washed and dried. No chlorine dioxide is formed during thebleaching and the product obtained is completely free from husks andstains and has a good degree of whiteness and excellent hydrophilicity.

The degree of hydrophilicity imparted by a bleaching process may beestimated by measuring the time required for a disc of fabric 20 mm. indiameter to become totally immersed in water at 20 C. after being laidon the surface. For example raw cotton satin bleached in a bathcontaining 3% of l30-volume hydrogen peroxide (based on the weight ofcotton) for minutes at 100 C., after washing and drying, takes longerthan 5 minutes to become totally immersed. When treated in accordancewith the present invention, and bleached in a bath containing only 2% of130-volume hydrogen peroxide for 10 minutes at 100 C. followed bywashing and drying, the same fabric has an immersion time of only 2seconds. Moreover, if the treatment with the chlorocyanuric compound isomitted, the preliminary treatment with amylase gives only a relativelyinsignificant improvement in hydrophilicity.

The following examples illustrate the invention.

EXAMPLE 1 A starch-sized, cotton poplin fabric 140 centimeters in widthand weighing 200 grams per meter was subjected to the process of theinvention without previous desizing. The fabric was fed to a caster-tankhaving a capacity of 20 meters of the fabric at a rate of 80 meters perminute. The bath contained 5 grams of amylase, 10 grams of sodiumchloride, and 1 gram of a wetting agent based on the octylester ofsulphosuccinic acid, per liter. The temperature of the bath was 70 C.and the immersion time seconds. The fabric was squeezed to a 70% wettake-up after leaving the tank and then fed to a washing tank containingwater at 100 C. and having a capacity of 15 to meters of the fabric.Amylase starch size were removed by this washing. The fabric was thensqueezed to a 55% wet take-up and fed to a second caster-tank containinga solution at 30 C. of 8.25 grams per liter of trichloroisocyanuricacid, 2.29 grams per liter of cyanuric acid, and 4.46 grams per liter ofsodium bicarbonate. The fabric remained in this tank for 15 seconds andwas then squeezed to 70% wet take-up and passed to a washing taiikcontaining water at 100 C., where it was washed for 10 seconds and theexcess isocyanuric acid derivative was removed. The fabric was thensqueezed to 55% wet take-up and passed to a third tank, it was soaked ina solution at 30 C. containing 15 grams per liter of sodium hydroxide,grams per liter of 36 B. sodium silicate solution, 7 grams per liter ofa wetting agent based on a condensate of a fatty acid with adepolymerized protein, and milliliters of aqueous hydrogen peroxide. Theconcentration of this bath was kept constant by adding to it asnecessary a solution containing the same ingredients in tripleconcentration. The fabric after leaving this bath was squeezed to a 75%wet take-up and then passed vertically through a steamer at 100 C. Itwas then fed to a maturing chamber having a capacity of 1000 meters andkept therein for 10 minutes at 100 C. The fabric was then passed to aseries of five washing tanks, the first of which contained sodiumhydroxide solution in a concentration of 10 grams per liter at 100 C.and the other four hot water.

Very white, completely desized fabric of excellent hydrophilicity wasobtained. The polymerization degree of the cellulose was reduced onlyfrom 2700 for the unbleached cotton to 2100 for the bleached fabric.

EXAMPLE 2 A starch-sized cream colored mixed fabric having a cotton warpand a thread-bleached linen woof Weighing 250 grams per square meter wassubjected to the treatment described in Example 1 at a rate of 50 metersper minute. The first tank contained 5 grams per liter of amylase, 10grams per liter of sodium chloride, and 2 grams per liter of non-ionicwetting agent. Its temperature was 60" C. The bath containing theisocyanuric acid derivative had a temperature of 40 C. and aconcentration 50% higher than that described in Example 1. The bleachingwith hydrogen peroxide was carried out under the conditions described inExample 1.

The fabric obtained had a degree of whiteness corresponding to white,was perfectly desized, and had a very good degree of hydrophilicity. Thepolymerization degree was reduced from 2100 to 1800. The non-cellulosicparts of the linen and the cotton husks were completely removed.

In this example, or in any of the other examples, the amylase employedcan be any commercially available amylase or amylase preparations knownas a textile desizing agent. Thus, use can be made of the commerciallyavailable Rapidase, a known textile desizing agent.

EXAMPLE 3 The fabric treated was a mixed polyester/cotton poplinintended for a resin treatment combined with waterproofing. The poplinweighed 120 grams per square meter and had a width of centimeters. Thetreatment with amylase was carried out at 70 C. for 20' seconds in abath containing 7 grams per liter of Rapidase, 10 grams per liter ofsodium chloride, and 1 gram per liter of a wetting agent based on analkyl-aryl sulphonate. After washing, the poplin was contacted for 20seconds with a bath at 20 C. containing 10 grams per liter of sodiumdichloroisocyanurate containing 60% of available chlorine. Washing andbleaching with hydrogen peroxide were carried out as in Example 1, thematuring time being only 5 minutes at C.

The treated fabric was completely desized and had a high degree ofwhiteness. The degree of polymerization of the cellulose was reducedfrom 2580 to 2050 and the hydrophilicity was such that the immersiontime of a fabric disc was 1 second.

EXAMPLE 4 A cotton twill fabric intended for vat dyeing on a jigger wastreated with amylase and a chlorocyanuric acid derivative as describedin. Example 1 and, after washing, was soaked in a solution containing 20grams per liter of sodium. hydroxide, 20 grams per liter of 36 B. sodiumsilicate solution, 5 grams per liter of a polymeric sodiummetaphosphate, and 50 milliliters of 35% aqueous hydrogen peroxidesolution. After squeezing to 100% wet take-up, the fabric was rolled upand rotated slowly for 10 hours at 20 C. The fabric was then unfoldedand washed. The husk and starch had been completely removed. The fabrichad a sufficient degree of whiteness for dyeing and very goodhydrophilicity. The polymerization degree of the cellulose was reducedfrom 2500 to 2100.

EXAMPLE 5 A starch-sized mixed cotton/polyamide fabric weighsqueezed to60% wet take-up. The fabric was then fed to a second castor-tank at 40C. containing 12.4 grams per liter of trichlorocyanuric acid, 3.3 gramsper liter of cyanuric acid, and 6.7 grams per liter of sodiumbicarbonate. The fabric was squeezed to 60% wet takeup and then passedunfolded into a washer having 3 tanks wherein the excess of thechlorocyanuric acid derivative was washed out with very hot water. Thefabric was then bleached by feeding into a tank containing 15 grams perliter of 100% sodium chlorite, and 3.6 grams per liter of monosodiumphosphate. The fabric was squeezed to 65% wet take-up and fed to asteamer at 100 C. The fabric was folded in a maturing vessel Where itwas kept for minutes at 100 C. When bleaching was completed, the fabricwas fedunfolded into a washer having four tanks, the first containinggrams per liter of sodium hydroxide and the other three very hot water.Fabric having good hydrophilicity and very high degree of whiteness wasobtained. All the size was removed and the mechanical strength of thefabric was reduced only by 5% compared with the unbleached fabric.

What is claimed is:

1. Continuous process for bleaching unbleached cellulose textilematerial which comprises contacting the said material with, in thefollowing order:

(1) an aqueous solution of amylase having a concentration of 2 to 10grams per liter at a temperature from about 20 to 80 C.

(2) an aqueous solution of chlorocyanuric compound containing 2 to 20grams per liter of available chlorine having a pH of 4 to 8 at atemperature from about 10 to 60 C., and

(3) an oxidative bleaching agent which is hydrogen peroxide or sodiumchlorite.

2. A process according to claim 1 wherein the chlorocyanuric compound issodium dichloroisocyanurate or trichloroisocyanuric acid.

3. A process according to claim 1 wherein the said unbleached materialis contacted for 5 to 30 seconds with the chlorocyanuric compound.

4. A process according to claim 1 wherein the said unbleached materialis contacted for 5 to 30 seconds with the aqueous solution of amylase.

5. A process according to claim 1 wherein the oxidative bleaching agentis hydrogen peroxide in the form of an aqueous solution containing 1 to3% by weight of 130 volume (35%) hydrogen peroxide, and the contact timeis V2 to 10 minutes.

6. A process according to claim 1 wherein the oxidative bleaching agentis soduim chlorite in the form of an aqueous solution having aconcentration of 10 to 30 grams per liter, and the contact time is 5 to15 minutes.

7. A process according to claim 1 wherein the cellulose textile materialis thoroughly washed before being contacted with the chlorocyanuriccompound and before being contacted with the oxidative bleaching agent.

8. A process according to claim 1 wherein the cellulose textile materialis subjected to an alkaline wash after treatment with the oxidativebleaching agent.

9. A process according to claim 1 wherein the cellulose textile materialis in the form of a continuous fabric which is treated continuously at arate of at least meters per minute.

References Cited UNITED STATES PATENTS 2,494,542 1/ 1950 Casciani 8-1062,898,333 8/ 1959 Oransroldsvik 8l0lX 2,903,327 9/ 1959 Rogers 8-1082,974,001 3/ 1961 Windbichler et a1 8-108 3,020,197 2/1962 Schuber162-89X MAYER WEINBLATI', Primary Examiner US. Cl. X.R.

